Cryptology ePrint Archive: Report 2001/035

Forward-Security in Private-Key Cryptography

Mihir Bellare and Bennet Yee

Abstract: This paper provides a comprehensive treatment of
forward-security in the context of shared-key based cryptographic primitives,
as a practical means to mitigate the damage caused by key-exposure. We provide
definitions of security, practical proven-secure constructions, and
applications for the main primitives in this area. We identify forward-secure
pseudorandom bit generators as the central primitive, providing several
constructions and then showing how forward-secure message authentication
schemes and symmetric encryption schemes can be built based on standard schemes
for these problems coupled with forward-secure pseudorandom bit generators. We
then apply forward-secure message authentication schemes to the problem of
maintaining secure access logs in the presence of break-ins.